This invention relates to improving the beam pattern of linear array transducers used in ultrasonic imaging systems.
Ultrasonic phased array sector scanners require a wide angular view, typically .+-.45.degree., for medical diagnostic and clinical applications. To meet this requirement, ultrasonic arrays are constructed from a large number of elements each of which exhibits a wide acceptance angle. The beam pattern for an individual array element which represents the ideal for imaging applications (see FIG. 1) is such that the beam is of uniform amplitude over the acceptance region and is zero outside this region. In practice, the ideal pattern is approximated by the diffraction pattern from a radiator (element) of dimension comparable to an ultrasonic wavelength. A typical beam pattern of an actual, practical array element (FIG. 2) exhibits the desirable feature that the amplitude is nearly uniform up to approximately 40.degree., but also has the undesirable feature that significant energy is directed outside the nominal acceptance region.
Substantial effort has been directed toward developing ultrasonic arrays whose elements exhibit beam patterns which approach the ideal pattern of FIG. 1. However, previous work in tailoring the beam pattern from individual array elements has focused on altering parameters which influence the diffraction patterns.